PUVA (psoralens plus ultraviolet A) is an effective therapy for psoriasis but often has systemic side-effects. We are testing whether bath water delivery of psoralens in conjunction with UVA is a safe and effective alternate route of therapy for psoriasis Systemic absorption of psoralen from bath water appears to be minimal, virtually eliminating potential systemic side effects. Bath water psoralens also produce high skin levels of this photosensitizer and the need for less UVA, thus possibly decreasing the risk of skin carcinogenicity.